Can addition of test sites for monofilament testing improve detection of nerve function impairment?

Summary

Background: In a multi-centre study titled ‘Treatment of Early Neuropathy in Leprosy’ (‘TENLEP’), monofilament testing (MFT) was used for the detection of touch pressure sensibility impairment (TPSI). It was recommended to use three test sites each for median, ulnar, radial cutaneous, sural and posterior tibial nerves. Aim: To assess the possible increase in detection rate of TPSI by increasing test sites for ulnar, median and posterior tibial nerves. Method and subjects: For the ulnar nerve, two sites were added in the area supplied by its dorsal cutaneous branch. For the median and posterior tibial nerve, one site each was added on dorsum of the index finger and heel respectively. Bilateral nerves were tested in a total of 70 leprosy patients. Findings: The addition of two extra test sites on the ulnar nerve resulted in the detection of TPSI in an additional 41 (29%) of the 140 nerves tested. Similarly for the median and posterior tibial nerves, the addition of one test site each detected TPSI in an additional 21 (15%) and 23 (16%) nerves respectively. Conclusion: The study showed that the addition of five test sites divided over three nerves, the ulnar, median and posterior tibial nerves, improved the detection of TPSI by 20%.